The macromolecular components of oral streptococci endowing them with the ability to specifically bind to human oral tissues are being studied. Bacteria included in these studies are Streptococcus mutans, an oral pathogen which is thought to achieve adherence to the tooth surface by synthesizing and binding water-insoluble adherent glucans, and Streptococcus sanguis, which appears to utilize host salivary and cell-surface glycoproteins to achieve specific adherence to the tooth surface or the oral epithelium. The several glucosyltransferases (GTF) elaborated by S. mutans comprise three distinct enzyme types. Sucrose-dependent cell-to-surface adherence appears to be mediated by one group of GTF, synthesizing insoluble glucan, while subsequent plaque formation requires a second, unique insoluble glucan-producing GTF which is not needed for cell to surface adherence. Two S. mutans lectins, on binding glucans and the second binding glycoproteins, may serve to attach cells to adherent glucan during sucrose-dependent adherence and to dental pellicle glycoproteins during sucrose-independent adherence, respectively. Continuing studies are directed to the conformation of the roles of these GTF enzymes and lectins in cell adherence and plaque formation by S. mutans. Glycoprotein-binding proteins of S. sanguis, previously identified, were not studied during the current year. It is planned to isolate these proteins, confirm their carbohydrate-binding abilities and determine their roles in cell to surface adherence mediated by salivary glycoproteins of the dental pellicle.